// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.AspNetCore.Razor.Language;
using Microsoft.AspNetCore.Razor.Language.Components;

namespace Microsoft.CodeAnalysis.Razor
{
    internal class ComponentTagHelperDescriptorProvider : RazorEngineFeatureBase, ITagHelperDescriptorProvider
    {
        private static readonly SymbolDisplayFormat FullNameTypeDisplayFormat =
            SymbolDisplayFormat.FullyQualifiedFormat
                .WithGlobalNamespaceStyle(SymbolDisplayGlobalNamespaceStyle.Omitted)
                .WithMiscellaneousOptions(SymbolDisplayFormat.FullyQualifiedFormat.MiscellaneousOptions & (~SymbolDisplayMiscellaneousOptions.UseSpecialTypes));

        public bool IncludeDocumentation { get; set; }

        public int Order { get; set; }

        public void Execute(TagHelperDescriptorProviderContext context)
        {
            if (context == null)
            {
                throw new ArgumentNullException(nameof(context));
            }

            var compilation = context.GetCompilation();
            if (compilation == null)
            {
                // No compilation, nothing to do.
                return;
            }

            var symbols = ComponentSymbols.Create(compilation);

            var types = new List<INamedTypeSymbol>();
            var visitor = new ComponentTypeVisitor(symbols, types);

            // Visit the primary output of this compilation, as well as all references.
            visitor.Visit(compilation.Assembly);
            foreach (var reference in compilation.References)
            {
                // We ignore .netmodules here - there really isn't a case where they are used by user code
                // even though the Roslyn APIs all support them.
                if (compilation.GetAssemblyOrModuleSymbol(reference) is IAssemblySymbol assembly)
                {
                    visitor.Visit(assembly);
                }
            }

            for (var i = 0; i < types.Count; i++)
            {
                var type = types[i];

                // Components have very simple matching rules.
                // 1. The type name (short) matches the tag name.
                // 2. The fully qualified name matches the tag name.
                var shortNameMatchingDescriptor = CreateShortNameMatchingDescriptor(symbols, type);
                context.Results.Add(shortNameMatchingDescriptor);
                var fullyQualifiedNameMatchingDescriptor = CreateFullyQualifiedNameMatchingDescriptor(symbols, type);
                context.Results.Add(fullyQualifiedNameMatchingDescriptor);

                foreach (var childContent in shortNameMatchingDescriptor.GetChildContentProperties())
                {
                    // Synthesize a separate tag helper for each child content property that's declared.
                    context.Results.Add(CreateChildContentDescriptor(symbols, shortNameMatchingDescriptor, childContent));
                    context.Results.Add(CreateChildContentDescriptor(symbols, fullyQualifiedNameMatchingDescriptor, childContent));
                }
            }
        }

        private TagHelperDescriptor CreateShortNameMatchingDescriptor(ComponentSymbols symbols, INamedTypeSymbol type)
        {
            var builder = CreateDescriptorBuilder(symbols, type);
            builder.TagMatchingRule(r =>
            {
                r.TagName = type.Name;
            });

            return builder.Build();
        }

        private TagHelperDescriptor CreateFullyQualifiedNameMatchingDescriptor(ComponentSymbols symbols, INamedTypeSymbol type)
        {
            var builder = CreateDescriptorBuilder(symbols, type);
            var containingNamespace = type.ContainingNamespace.ToDisplayString();
            var fullName = $"{containingNamespace}.{type.Name}";
            builder.TagMatchingRule(r =>
            {
                r.TagName = fullName;
            });
            builder.Metadata[ComponentMetadata.Component.NameMatchKey] = ComponentMetadata.Component.FullyQualifiedNameMatch;

            return builder.Build();
        }

        private TagHelperDescriptorBuilder CreateDescriptorBuilder(ComponentSymbols symbols, INamedTypeSymbol type)
        {
            var typeName = type.ToDisplayString(FullNameTypeDisplayFormat);
            var assemblyName = type.ContainingAssembly.Identity.Name;

            var builder = TagHelperDescriptorBuilder.Create(ComponentMetadata.Component.TagHelperKind, typeName, assemblyName);
            builder.SetTypeName(typeName);
            builder.CaseSensitive = true;

            // This opts out this 'component' tag helper for any processing that's specific to the default
            // Razor ITagHelper runtime.
            builder.Metadata[TagHelperMetadata.Runtime.Name] = ComponentMetadata.Component.RuntimeName;

            if (type.IsGenericType)
            {
                builder.Metadata[ComponentMetadata.Component.GenericTypedKey] = bool.TrueString;

                for (var i = 0; i < type.TypeArguments.Length; i++)
                {
                    var typeParameter = type.TypeArguments[i] as ITypeParameterSymbol;
                    if (typeParameter != null)
                    {
                        CreateTypeParameterProperty(builder, typeParameter);
                    }
                }
            }

            var xml = type.GetDocumentationCommentXml();
            if (!string.IsNullOrEmpty(xml))
            {
                builder.Documentation = xml;
            }

            foreach (var property in GetProperties(symbols, type))
            {
                if (property.kind == PropertyKind.Ignored)
                {
                    continue;
                }

                CreateProperty(builder, property.property, property.kind);
            }

            if (builder.BoundAttributes.Any(a => a.IsParameterizedChildContentProperty()) &&
                !builder.BoundAttributes.Any(a => string.Equals(a.Name, ComponentMetadata.ChildContent.ParameterAttributeName, StringComparison.OrdinalIgnoreCase)))
            {
                // If we have any parameterized child content parameters, synthesize a 'Context' parameter to be
                // able to set the variable name (for all child content). If the developer defined a 'Context' parameter
                // already, then theirs wins.
                CreateContextParameter(builder, childContentName: null);
            }

            return builder;
        }

        private void CreateProperty(TagHelperDescriptorBuilder builder, IPropertySymbol property, PropertyKind kind)
        {
            builder.BindAttribute(pb =>
            {
                pb.Name = property.Name;
                pb.TypeName = property.Type.ToDisplayString(FullNameTypeDisplayFormat);
                pb.SetPropertyName(property.Name);

                if (kind == PropertyKind.Enum)
                {
                    pb.IsEnum = true;
                }

                if (kind == PropertyKind.ChildContent)
                {
                    pb.Metadata.Add(ComponentMetadata.Component.ChildContentKey, bool.TrueString);
                }

                if (kind == PropertyKind.EventCallback)
                {
                    pb.Metadata.Add(ComponentMetadata.Component.EventCallbackKey, bool.TrueString);
                }

                if (kind == PropertyKind.Delegate)
                {
                    pb.Metadata.Add(ComponentMetadata.Component.DelegateSignatureKey, bool.TrueString);
                }

                if (HasTypeParameter(property.Type))
                {
                    pb.Metadata.Add(ComponentMetadata.Component.GenericTypedKey, bool.TrueString);
                }

                var xml = property.GetDocumentationCommentXml();
                if (!string.IsNullOrEmpty(xml))
                {
                    pb.Documentation = xml;
                }
            });

            bool HasTypeParameter(ITypeSymbol type)
            {
                if (type is ITypeParameterSymbol)
                {
                    return true;
                }

                // We need to check for cases like:
                // [Parameter] public List<T> MyProperty { get; set; }
                // AND
                // [Parameter] public List<string> MyProperty { get; set; }
                //
                // We need to inspect the type arguments to tell the difference between a property that
                // uses the containing class' type parameter(s) and a vanilla usage of generic types like
                // List<> and Dictionary<,>
                //
                // Since we need to handle cases like RenderFragment<List<T>>, this check must be recursive.
                if (type is INamedTypeSymbol namedType && namedType.IsGenericType)
                {
                    var typeArguments = namedType.TypeArguments;
                    for (var i = 0; i < typeArguments.Length; i++)
                    {
                        if (HasTypeParameter(typeArguments[i]))
                        {
                            return true;
                        }
                    }

                    // Another case to handle - if the type being inspected is a nested type
                    // inside a generic containing class. The common usage for this would be a case
                    // where a generic templated component defines a 'context' nested class.
                    if (namedType.ContainingType != null && HasTypeParameter(namedType.ContainingType))
                    {
                        return true;
                    }
                }

                return false;
            }
        }

        private void CreateTypeParameterProperty(TagHelperDescriptorBuilder builder, ITypeSymbol typeParameter)
        {
            builder.BindAttribute(pb =>
            {
                pb.DisplayName = typeParameter.Name;
                pb.Name = typeParameter.Name;
                pb.TypeName = typeof(Type).FullName;
                pb.SetPropertyName(typeParameter.Name);

                pb.Metadata[ComponentMetadata.Component.TypeParameterKey] = bool.TrueString;

                pb.Documentation = string.Format(ComponentResources.ComponentTypeParameter_Documentation, typeParameter.Name, builder.Name);
            });
        }

        private TagHelperDescriptor CreateChildContentDescriptor(ComponentSymbols symbols, TagHelperDescriptor component, BoundAttributeDescriptor attribute)
        {
            var typeName = component.GetTypeName() + "." + attribute.Name;
            var assemblyName = component.AssemblyName;

            var builder = TagHelperDescriptorBuilder.Create(ComponentMetadata.ChildContent.TagHelperKind, typeName, assemblyName);
            builder.SetTypeName(typeName);
            builder.CaseSensitive = true;

            // This opts out this 'component' tag helper for any processing that's specific to the default
            // Razor ITagHelper runtime.
            builder.Metadata[TagHelperMetadata.Runtime.Name] = ComponentMetadata.ChildContent.RuntimeName;

            // Opt out of processing as a component. We'll process this specially as part of the component's body.
            builder.Metadata[ComponentMetadata.SpecialKindKey] = ComponentMetadata.ChildContent.TagHelperKind;

            var xml = attribute.Documentation;
            if (!string.IsNullOrEmpty(xml))
            {
                builder.Documentation = xml;
            }

            // Child content matches the property name, but only as a direct child of the component.
            builder.TagMatchingRule(r =>
            {
                r.TagName = attribute.Name;
                r.ParentTag = component.TagMatchingRules.First().TagName;
            });

            if (attribute.IsParameterizedChildContentProperty())
            {
                // For child content attributes with a parameter, synthesize an attribute that allows you to name
                // the parameter.
                CreateContextParameter(builder, attribute.Name);
            }

            if (component.IsComponentFullyQualifiedNameMatch())
            {
                builder.Metadata[ComponentMetadata.Component.NameMatchKey] = ComponentMetadata.Component.FullyQualifiedNameMatch;
            }

            var descriptor = builder.Build();

            return descriptor;
        }

        private void CreateContextParameter(TagHelperDescriptorBuilder builder, string childContentName)
        {
            builder.BindAttribute(b =>
            {
                b.Name = ComponentMetadata.ChildContent.ParameterAttributeName;
                b.TypeName = typeof(string).FullName;
                b.Metadata.Add(ComponentMetadata.Component.ChildContentParameterNameKey, bool.TrueString);
                b.Metadata.Add(TagHelperMetadata.Common.PropertyName, b.Name);

                if (childContentName == null)
                {
                    b.Documentation = ComponentResources.ChildContentParameterName_TopLevelDocumentation;
                }
                else
                {
                    b.Documentation = string.Format(ComponentResources.ChildContentParameterName_Documentation, childContentName);
                }
            });
        }

        // Does a walk up the inheritance chain to determine the set of parameters by using
        // a dictionary keyed on property name.
        //
        // We consider parameters to be defined by properties satisfying all of the following:
        // - are public
        // - are visible (not shadowed)
        // - have the [Parameter] attribute
        // - have a setter, even if private
        // - are not indexers
        private IEnumerable<(IPropertySymbol property, PropertyKind kind)> GetProperties(ComponentSymbols symbols, INamedTypeSymbol type)
        {
            var properties = new Dictionary<string, (IPropertySymbol, PropertyKind)>(StringComparer.Ordinal);
            do
            {
                if (SymbolEqualityComparer.Default.Equals(type, symbols.ComponentBase))
                {
                    // The ComponentBase base class doesn't have any [Parameter].
                    // Bail out now to avoid walking through its many members, plus the members
                    // of the System.Object base class.
                    break;
                }

                var members = type.GetMembers();
                for (var i = 0; i < members.Length; i++)
                {
                    var property = members[i] as IPropertySymbol;
                    if (property == null)
                    {
                        // Not a property
                        continue;
                    }

                    if (properties.ContainsKey(property.Name))
                    {
                        // Not visible
                        continue;
                    }

                    var kind = PropertyKind.Default;
                    if (property.DeclaredAccessibility != Accessibility.Public)
                    {
                        // Not public
                        kind = PropertyKind.Ignored;
                    }

                    if (property.Parameters.Length != 0)
                    {
                        // Indexer
                        kind = PropertyKind.Ignored;
                    }

                    if (property.SetMethod == null)
                    {
                        // No setter
                        kind = PropertyKind.Ignored;
                    }
                    else if (property.SetMethod.DeclaredAccessibility != Accessibility.Public)
                    {
                        // No public setter
                        kind = PropertyKind.Ignored;
                    }

                    if (property.IsStatic)
                    {
                        kind = PropertyKind.Ignored;
                    }

                    if (!property.GetAttributes().Any(a => SymbolEqualityComparer.Default.Equals(a.AttributeClass, symbols.ParameterAttribute)))
                    {
                        if (property.IsOverride)
                        {
                            // This property does not contain [Parameter] attribute but it was overridden. Don't ignore it for now.
                            // We can ignore it if the base class does not contains a [Parameter] as well.
                            continue;
                        }

                        // Does not have [Parameter]
                        kind = PropertyKind.Ignored;
                    }

                    if (kind == PropertyKind.Default && property.Type.TypeKind == TypeKind.Enum)
                    {
                        kind = PropertyKind.Enum;
                    }

                    if (kind == PropertyKind.Default && SymbolEqualityComparer.Default.Equals(property.Type, symbols.RenderFragment))
                    {
                        kind = PropertyKind.ChildContent;
                    }

                    if (kind == PropertyKind.Default &&
                        property.Type is INamedTypeSymbol namedType &&
                        namedType.IsGenericType &&
                        SymbolEqualityComparer.Default.Equals(namedType.ConstructedFrom, symbols.RenderFragmentOfT))
                    {
                        kind = PropertyKind.ChildContent;
                    }

                    if (kind == PropertyKind.Default && SymbolEqualityComparer.Default.Equals(property.Type, symbols.EventCallback))
                    {
                        kind = PropertyKind.EventCallback;
                    }

                    if (kind == PropertyKind.Default &&
                        property.Type is INamedTypeSymbol namedType2 &&
                        namedType2.IsGenericType &&
                        SymbolEqualityComparer.Default.Equals(namedType2.ConstructedFrom, symbols.EventCallbackOfT))
                    {
                        kind = PropertyKind.EventCallback;
                    }

                    if (kind == PropertyKind.Default && property.Type.TypeKind == TypeKind.Delegate)
                    {
                        kind = PropertyKind.Delegate;
                    }

                    properties.Add(property.Name, (property, kind));
                }

                type = type.BaseType;
            }
            while (type != null);

            return properties.Values;
        }

        private enum PropertyKind
        {
            Ignored,
            Default,
            Enum,
            ChildContent,
            Delegate,
            EventCallback,
        }

        private class ComponentSymbols
        {
            public static ComponentSymbols Create(Compilation compilation)
            {
                // We find a bunch of important and fundamental types here that are needed to discover
                // components. If one of these isn't defined then we just bail, because the results will
                // be unpredictable.
                var symbols = new ComponentSymbols();

                symbols.ComponentBase = compilation.GetTypeByMetadataName(ComponentsApi.ComponentBase.MetadataName);
                if (symbols.ComponentBase == null)
                {
                    // No definition for ComponentBase, nothing to do.
                    return null;
                }

                symbols.IComponent = compilation.GetTypeByMetadataName(ComponentsApi.IComponent.MetadataName);
                if (symbols.IComponent == null)
                {
                    // No definition for IComponent, nothing to do.
                    return null;
                }

                symbols.ParameterAttribute = compilation.GetTypeByMetadataName(ComponentsApi.ParameterAttribute.MetadataName);
                if (symbols.ParameterAttribute == null)
                {
                    // No definition for [Parameter], nothing to do.
                    return null;
                }

                symbols.RenderFragment = compilation.GetTypeByMetadataName(ComponentsApi.RenderFragment.MetadataName);
                if (symbols.RenderFragment == null)
                {
                    // No definition for RenderFragment, nothing to do.
                    return null;
                }

                symbols.RenderFragmentOfT = compilation.GetTypeByMetadataName(ComponentsApi.RenderFragmentOfT.MetadataName);
                if (symbols.RenderFragmentOfT == null)
                {
                    // No definition for RenderFragment<T>, nothing to do.
                    return null;
                }

                symbols.EventCallback = compilation.GetTypeByMetadataName(ComponentsApi.EventCallback.MetadataName);
                if (symbols.EventCallback == null)
                {
                    // No definition for EventCallback, nothing to do.
                    return null;
                }

                symbols.EventCallbackOfT = compilation.GetTypeByMetadataName(ComponentsApi.EventCallbackOfT.MetadataName);
                if (symbols.EventCallbackOfT == null)
                {
                    // No definition for EventCallback<T>, nothing to do.
                    return null;
                }

                return symbols;
            }

            private ComponentSymbols()
            {
            }

            public INamedTypeSymbol ComponentBase { get; private set; }

            public INamedTypeSymbol IComponent { get; private set; }

            public INamedTypeSymbol ParameterAttribute { get; private set; }

            public INamedTypeSymbol RenderFragment { get; private set; }

            public INamedTypeSymbol RenderFragmentOfT { get; private set; }

            public INamedTypeSymbol EventCallback { get; private set; }

            public INamedTypeSymbol EventCallbackOfT { get; private set; }
        }

        private class ComponentTypeVisitor : SymbolVisitor
        {
            private readonly ComponentSymbols _symbols;
            private readonly List<INamedTypeSymbol> _results;

            public ComponentTypeVisitor(ComponentSymbols symbols, List<INamedTypeSymbol> results)
            {
                _symbols = symbols;
                _results = results;
            }

            public override void VisitNamedType(INamedTypeSymbol symbol)
            {
                if (IsComponent(symbol))
                {
                    _results.Add(symbol);
                }
            }

            public override void VisitNamespace(INamespaceSymbol symbol)
            {
                foreach (var member in symbol.GetMembers())
                {
                    Visit(member);
                }
            }

            public override void VisitAssembly(IAssemblySymbol symbol)
            {
                // This as a simple yet high-value optimization that excludes the vast majority of
                // assemblies that (by definition) can't contain a component.
                if (symbol.Name != null && !symbol.Name.StartsWith("System.", StringComparison.Ordinal))
                {
                    Visit(symbol.GlobalNamespace);
                }
            }

            internal bool IsComponent(INamedTypeSymbol symbol)
            {
                if (_symbols == null)
                {
                    return false;
                }

                var isComponent = ComponentDetectionConventions.IsComponent(symbol, _symbols.IComponent);
                return isComponent;
            }
        }
    }
}